+
+ return data;
+}
+
+uint32_t opb_read32(OPBus *opb, hwaddr addr)
+{
+ MemTxResult tx;
+ uint32_t data;
+
+ tx = opb_read(opb, addr, &data, sizeof(data));
+ /* FIXME: improve error handling */
+ assert(!tx);
+
+ return data;
+}
+
+static MemTxResult opb_write(OPBus *opb, hwaddr addr, void *data,
size_t len)
+{
+ return address_space_write(&opb->as, addr,
MEMTXATTRS_UNSPECIFIED, data,
+ len);
+}
+
+void opb_write8(OPBus *opb, hwaddr addr, uint8_t data)
+{
+ MemTxResult tx;
+
+ tx = opb_write(opb, addr, &data, sizeof(data));
+ /* FIXME: improve error handling */
+ assert(!tx);
+}
+
+void opb_write16(OPBus *opb, hwaddr addr, uint16_t data)
+{
+ MemTxResult tx;
+
+ tx = opb_write(opb, addr, &data, sizeof(data));
+ /* FIXME: improve error handling */
+ assert(!tx);
+}
+
+void opb_write32(OPBus *opb, hwaddr addr, uint32_t data)
+{
+ MemTxResult tx;
+
+ tx = opb_write(opb, addr, &data, sizeof(data));
+ /* FIXME: improve error handling */
+ assert(!tx);
+}
+
+void opb_fsi_master_address(OPBus *opb, hwaddr addr)
+{
+ memory_region_transaction_begin();
+ memory_region_set_address(&opb->fsi.iomem, addr);
+ memory_region_transaction_commit();
+}
+
+void opb_opb2fsi_address(OPBus *opb, hwaddr addr)
+{
+ memory_region_transaction_begin();
+ memory_region_set_address(&opb->fsi.opb2fsi, addr);
+ memory_region_transaction_commit();
+}
+
+static uint64_t opb_unimplemented_read(void *opaque, hwaddr addr,
unsigned size)
+{
+ qemu_log_mask(LOG_UNIMP, "%s: read @0x%" HWADDR_PRIx " size=%d\n",
+ __func__, addr, size);
+
+ return 0;
+}
+
+static void opb_unimplemented_write(void *opaque, hwaddr addr,
uint64_t data,
+ unsigned size)
+{
+ qemu_log_mask(LOG_UNIMP, "%s: write @0x%" HWADDR_PRIx " size=%d "
+ "value=%"PRIx64"\n", __func__, addr, size, data);
+}
+
+static const struct MemoryRegionOps opb_unimplemented_ops = {
+ .read = opb_unimplemented_read,
+ .write = opb_unimplemented_write,
+ .endianness = DEVICE_BIG_ENDIAN,
+};
+
+static void opb_realize(BusState *bus, Error **errp)
+{
+ OPBus *opb = OP_BUS(bus);
+ Error *err = NULL;
+
+ memory_region_init_io(&opb->mr, OBJECT(opb),
&opb_unimplemented_ops, opb,
+ NULL, UINT32_MAX);
+ address_space_init(&opb->as, &opb->mr, "opb");
+
+ object_property_set_bool(OBJECT(&opb->fsi), "realized", true,
&err);
+ if (err) {
+ error_propagate(errp, err);
+ return;
+ }
+ memory_region_add_subregion(&opb->mr, 0x80000000, &opb->fsi.iomem);
+
+ /* OPB2FSI region */
+ /*
+ * Avoid endianness issues by mapping each slave's memory region
directly.
+ * Manually bridging multiple address-spaces causes endian swapping
+ * headaches as memory_region_dispatch_read() and
+ * memory_region_dispatch_write() correct the endianness based
on the
+ * target machine endianness and not relative to the device
endianness on
+ * either side of the bridge.
+ */
+ /*
+ * XXX: This is a bit hairy and will need to be fixed when I
sort out the
+ * bus/slave relationship and any changes to the CFAM modelling
(multiple
+ * slaves, LBUS)
+ */
+ memory_region_add_subregion(&opb->mr, 0xa0000000,
&opb->fsi.opb2fsi);
+}
+
+static void opb_init(Object *o)
+{
+ OPBus *opb = OP_BUS(o);
+
+ object_initialize_child(o, "fsi-master", &opb->fsi,
TYPE_FSI_MASTER);
+ qdev_set_parent_bus(DEVICE(&opb->fsi), BUS(o), &error_abort);
+}
+
+static void opb_finalize(Object *o)
+{
+ OPBus *opb = OP_BUS(o);
+
+ address_space_destroy(&opb->as);
+}
+
+static void opb_class_init(ObjectClass *klass, void *data)
+{
+ BusClass *bc = BUS_CLASS(klass);
+ bc->realize = opb_realize;
+}
+
+static const TypeInfo opb_info = {
+ .name = TYPE_OP_BUS,
+ .parent = TYPE_BUS,
+ .instance_init = opb_init,
+ .instance_finalize = opb_finalize,
+ .instance_size = sizeof(OPBus),
+ .class_init = opb_class_init,
+ .class_size = sizeof(OPBusClass),
+};
+
+static void opb_register_types(void)
+{
+ type_register_static(&opb_info);
+}
+
+type_init(opb_register_types);
diff --git a/include/hw/fsi/opb.h b/include/hw/fsi/opb.h
new file mode 100644
index 0000000000..f8ce00383e
--- /dev/null
+++ b/include/hw/fsi/opb.h
@@ -0,0 +1,43 @@
+/*
+ * SPDX-License-Identifier: GPL-2.0-or-later
+ * Copyright (C) 2023 IBM Corp.
+ *
+ * IBM On-Chip Peripheral Bus
+ */
+#ifndef FSI_OPB_H
+#define FSI_OPB_H
+
+#include "exec/memory.h"
+#include "hw/fsi/fsi-master.h"
+
+#define TYPE_OP_BUS "opb"
+OBJECT_DECLARE_SIMPLE_TYPE(OPBus, OP_BUS)
+
+typedef struct OPBus {
+ /*< private >*/
+ BusState bus;
+
+ /*< public >*/
+ MemoryRegion mr;
+ AddressSpace as;
+
+ /* Model OPB as dumb enough just to provide an address-space */
+ /* TODO: Maybe don't store device state in the bus? */
+ FSIMasterState fsi;
+} OPBus;
+
+typedef struct OPBusClass {
+ BusClass parent_class;
+} OPBusClass;
+
+uint8_t opb_read8(OPBus *opb, hwaddr addr);
+uint16_t opb_read16(OPBus *opb, hwaddr addr);
+uint32_t opb_read32(OPBus *opb, hwaddr addr);
+void opb_write8(OPBus *opb, hwaddr addr, uint8_t data);
+void opb_write16(OPBus *opb, hwaddr addr, uint16_t data);
+void opb_write32(OPBus *opb, hwaddr addr, uint32_t data);
+
+void opb_fsi_master_address(OPBus *opb, hwaddr addr);
+void opb_opb2fsi_address(OPBus *opb, hwaddr addr);
+
+#endif /* FSI_OPB_H */